173 



PARHELIA MILLANIANA. 

 (a rejoinder.) 



By Dr. James Stirton. 



In reference to the Reyd. W. Leigliton's remarks under Parmelia 

 Millaniana in the preceding number of this Journal (p. 117), per- 

 haps I may be allowed, as on a similar occasion lately, to put in a 

 plea on my own behalf. 



At page 140 of Mr. Leighton's " Lich. Flora" is given the diagnosis 

 of P. endochlora, and at page 79 of the 26th number of Grevillea 

 is given that of P. Millaniana. 



In order to compare, or rather contrast, more succinctly the two 

 descriptions, the various items are here given in a tabulated form. 



P. endochlora. P. Millaniana 



TLallua whitish. Thallus albido-glaucescent. 



,, very uneven. ,, smooth. 



,, tuberculoso — nigricanti — so ,, no soredia whatever, 

 rediate. 



Medulla yellow. Medulla, pale, yellow, thin. 



Ehizicse not mentioned, a presumption Rhizinse, branching in a tree-like form 



being afforded that there is nothing from a common stock, 

 peculiar about them. 



In order to show the contrast more completely, Mr. Leighton 

 says that K. produces a yellowish brown re- action on P. endochlora, 

 while the same re-agent does not produce the slightest change of 

 tint in P. Millaniana, but merely, as in many other cases, swells 

 the medullary fibres, and renders them more transparent and gela- 

 tinous. On the other hand C. produces instantaneously a clear, 

 bright yellow, &c. (see description). Such a contrast in the 

 chemical re-actions appears to me to be of itself quite sufficient to 

 keep the two lichens distinct. I may add that P. Millaniana was 

 exhibited before the Glasgow Society of Field Naturalists, and its 

 diagnosis recorded in the minutes nearly a month before Mr. 

 Leighton's decision was arrived at. 



In view of such manifest differences, I had no hesitation in 

 separating the two lichens, and I have as little hesitation now. 



Mr. Leighton's criticisms on Lecidea emphysa in the next para- 

 graph require, also, some consideration. In the first place he has 

 quite mistaken the purport of my remarks on it in two particulars. 

 1st — I did not allude to the mutual re- actions of potash and iodine 

 on one another, which, quoad the lichen, are worthless ; but of each 

 re-agent in succession on two organic substances, viz., the so-called 

 chrysophanic acid and the hymenial gelatine. After the chryso- 

 phanic acid had been changed in constitution and dissolved out by 

 means of liq. potassse, and the addition of abundance of water to 

 clear off the solution, iodine was added, not only to neutralize any 

 potash that may have remained, but to saturate the whole hymenium. 



